another point, the application of da adiabatic process cud b used for the sheath of air around the hand. as the air from da narrow opening comes out it has more k.e. hence, vit displaces the air around da hand over a larger area hence, lowering da temp, which isnt done in da bigger opening. this case can b seen as one of perfect overlap in da case of the wide opening and of irregularity in da case of da narrow 1.